Search for higher oxides of Pu: A photoemission study

Gouder, T.; Seibert, Α.; Havela, L.; Rébizant, J.

doi:10.1016/j.susc.2007.04.259

Cited by 54 publications

(62 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[3]), which does not seem to reproduce well e.g. photoelectron spectra [4]. Here we have to look back a bit and ask how much we generally understand the 5f magnetism, with large orbital moments induced in itinerant states by strong spin-orbit interaction, what is the relation of the 5f bonding and magnetic anisotropy, affecting not only directions of ordered moments but also determining the type of magnetic fluctuations in the paramagnetic state.…”

Section: Introductionmentioning

confidence: 99%

UH3-based ferromagnets: New look at an old material

Havela

Paukov

Tkach

et al. 2016

Journal of Magnetism and Magnetic Materials

Self Cite

View full text Add to dashboard Cite

UH 3 is the first discovered material with ferromagnetism based purely on the 5f electronic states, known for more than half century. Although the U metal is Pauli paramagnet, the reduced 5f-5f overlap in compounds allows for moment formation and ordering, typically if the U-U spacing exceeds the Hill limit, i.e. about 340 pm. The stable form of UH 3 , known as β-UH 3 , has rather high T C ≈ 170 K. Such high value is rather unusual, considering d U-U = 331 pm. Properties of metastable α-UH 3 with d U-U = 360 pm could be never well established. Using the fact that α-UH 3 is in fact bcc U with interstitials filled by H, we attempted to synthesize α-UH 3 starting from the γ-U alloys, with the bcc structure retained to room temperature by doping combined with ultrafast cooling. While up to 15% Zr a contamination by β-UH 3 was obtained, 20% Zr yielded single phase α-UH 3 . The T C value remains high and very similar to β-UH 3 . One can see an increase up to 187 K for 15% Zr, followed by a weak decrease. Magnetic moments remain close to 1 μ B /U atom. An insight is provided by ab-initio calculations, revealing a a charge transfer towards H-1s states, depopulating the U-6d and 7s states, leaving almost pure 5f character around the Fermi level. The 5f magnetism exhibits a high coercivity (μ 0 H c up to 5.5 T) and large spontaneous volume magnetostriction of 3.2*10 -3 . Even higher increase of T C , reaching up to 203 K, can be achieved in analogous Mo stabilized hydrides, which yield an amorphous structure. The compounds represent, together with known hydrides of U 6 Fe and U 6 Co, a new group of robust 5f ferromagnets with small d U-U but high T C . Although common hydrides are fine powders, some of the new hydrides described as (UH 3 ) (1-x) T x (T = Zr or Mo) remain monolithic, which allows to study transport and thermodynamic properties.

show abstract

Section: Introductionmentioning

confidence: 99%

UH3-based ferromagnets: New look at an old material

Havela

Paukov

Tkach

et al. 2016

Journal of Magnetism and Magnetic Materials

Self Cite

View full text Add to dashboard Cite

show abstract

“…Adsorption energies of water on differently oriented uranium dioxide planes were calculated. 14, 15,16 The work on the study of the electronic structure of uranium and its alloys [17][18][19][20][21] and oxides UO 2+x (x≤0 and x≥0) employed theoretical calculation results, [22][23][24][25][26][27][28][29][30][31][32][33][34] photoelectron spectroscopy (PES) [35][36][37][38][39][40][41] and X-ray photoelectron spectroscopy (XPS) widely. 38,[42][43][44][45][46][47][48][49][50][51][52][53][54][55] These techniques were used to study films on various substrates.…”

Section: Introductionmentioning

confidence: 99%

XPS Study of Ion Irradiated and Unirradiated UO₂ Thin Films

et al. 2016

View full text Add to dashboard Cite

XPS determination of the oxygen coefficient k O =2+x and ionic (U 4+ , U 5+ and U 6+ ) composition of oxides UO 2+x formed on the surfaces of differently oriented (hkl) planes of thin UO 2 films on LSAT (Al 10 La 3 O 51 Sr 14 Ta 7 ) and YSZ (yttria-stabilized zirconia) substrates was performed. The U 4f and O 1s core-electron peak intensities as well as the U 5f relative intensity before and after the 129 Xe 23+ and 238 U 31+ irradiations were employed. It was found that the presence of uranium dioxide film in air results in formation of oxide UO 2+x on the surface with mean oxygen coefficients k O in the range 2.07-2.11 on LSAT and 2.17-2.23 on YSZ substrates. These oxygen coefficients depend on the substrate and weakly on the crystallographic orientation.On the basis of the spectral parameters it was established that uranium dioxide films AP2,3 on the LSAT substrates have the smallest k O values, and from the XRD and EBSD results it follows that these samples have a regular monocrystalline structure. The XRD and EBSD results indicate that samples AP5-7 on the YSZ substrates have monocrystalline structure, however, they have the highest k O values. The observed difference in the k O values, probably, caused by the different nature of the substrates: the YSZ substrates provide 6.4% compressive strain, whereas (001) LSAT substrates result only in 0.03% tensile strain in the UO 2 films.129 Xe 23+ irradiation (92 MeV, 4.8 × 10 15 ions/cm 2 ) of uranium dioxide films on the LSAT substrates was shown to destroy both long range ordering and uranium close environment, which results in increase of uranium oxidation state and regrouping of oxygen ions in uranium close environment. 238 U 31+ (110 MeV, 5 × 10 10 , 5 × 10 11 , 5 × 10 12 ions/cm 2 ) irradiations of uranium dioxide films on the YSZ substrates were shown to form the lattice damage only with partial destruction of the long range ordering.3

show abstract

“…Plutonium dioxide (PuO 2 ) is an important ingredient of a mixed oxide (MOX) fuel for fast breeder reactors, the physical, chemical, and mechanical properties of which are important for nuclear engineering [9][10][11]. Also, PuO 2 has long been the compound of choice for plutonium reuse, separation, and deposition in long-term repositories, due to its reliable stability with respect to oxidation [12]. Based on these backgrounds, many studies have been performed to investigate various properties of PuO 2 [3][4][5][6][7][8][13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%